An x-ray diagnostics facility for implementing a method of this type is known from DE 100 37 735 A1 and is shown in FIG. 1 for instance, which features a C-arc 2 which is mounted in a rotatable fashion on a stator 1, on the ends of which C-arc 2 are attached an x-ray emitter 3 and an x-ray image detector 4.
Floor and/or ceiling stands can also be used instead of the stator 1 illustrated. The C-arc 2 can also be replaced by a so-called electronic C-arc 2, with which an electronic coupling between the x-ray emitter 3 and x-ray image detector 4 is carried out. The moveable components 2 to 5 can also be mounted on robot arms individually or together.
The x-ray image detector 4 can be a rectangular or quadratic flat semiconductor detector, which is preferably created from amorphous silicon (aSi).
A patient support table 5 for accommodating a patient for instance to carry out an examination of his/her heart is positioned in the radiation path of the x-ray emitter 3. An image system 6 is connected to the x-ray diagnostics facility, said image system 6 receiving and processing the image signals of the x-ray image detector 4.
Operations on patients are, to an increasing degree, becoming minimally invasive by introducing a catheter or another medical instrument using x-ray control through the bloodstream to the diseased part of the body for instance. Tumors, aneurysms, AVMs (arterio venous malformations) and stenoses are thus treated inter alia. The navigation of the catheter from the point of entry into the body to the site of the disease presents a huge challenge even for experienced medics. Navigation in the neural region is to be emphasized here since the targeted control in the filigran branched vascular system of the brain is highly demanding.
The problem here is that the catheter is indeed clearly visible during the fluoroscopy, but the anatomy of the patient, in particular their vascular structure, is in contrast hardly visible or possibly only visible after the injection of a contrast agent. The greatest problem with this procedure by the use for instance of the so-called “roadmap” and/or DSA functionality is that no spatial depth information is available, as can be inferred for instance from FIG. 2, which shows a classical “roadmap” image of a C-arc system according to FIG. 1, in which any depth information is absent. It is not obvious whether a vessel runs parallel to the observer, “going into the image” or “coming out of the image”. “Roadmap” images are knowingly generated by subtracting so-called post-injection images, i.e. recordings using a contrast agent, so-called blank images, i.e. recordings without a contrast agent. They only show the veins filled with contrast agent, so that the doctor is able to orientate himself to them when the “roadmap” images are superimposed with fluoroscopy images.
Because the use in recent years of 3D image data records, as described for instance in the brochure “LEONARDO—Intelligent Postprocessing/Intelligent Investment./Reliable Planning./Efficient Usage.”, by Siemens Medical Solutions, 2004, Order No.: A91100-M2040-B142-1-7600, became the prior art and are generally available, the aim is to use the 3D data record of the patient for navigation purposes. FIGS. 3 and 4 show a 3D volume of this type from two different views. The image in FIG. 4 is a lateral view from the right relative to the line of sight of the image according to FIG. 3. The marked areas point out particular sites to which reference is made in conjunction with the FIGS. 11 and 12.
With the aid of the classical “roadmap” functionality and a biplane C-arc system, for instance Siemens Artis dBA, described in the brochure “AXIOM Artis dBA/The soloist's duet for neuroradiology and universal angiography” by Siemens Medical Solutions, 2004, Order No. A91100-M1400-C824-1-7600, two Roadmap/DSA images which lie at an angle from one another are obtained simultaneously. The treating doctor is now able, on grounds of his experience, to extract spatial 3D information from these two images without depth information at least in the region in which he is currently interested. Finally, the possibilities of taking a three dimensional image of the vascular structure is however very limited.
With the aid of a 3D data record, the treating medic is now able to view the three-dimensional vascular structure, by allowing the 3D data record to be rotated on its 3D workstation and thus to be observed from different lines of sight (see FIGS. 3 and 4). But what he/she is lacking is the direct correspondence between the current x-ray image with the region of interest to him/her and the corresponding site in the 3D volume.
A method of this type, which reproduces these correspondences, is described for instance in the former patent application DE 10 2006 020 398.4.
A further alternative is one of superimposing the x-ray image with a corresponding projection of the 3D data record, as is shown for instance in FIG. 5. This is a quantum leap, but it only inadequately solves the problem of whether a vessel at a specific site runs parallel to the observer “going into the image” or “coming out of the image”. It is also only visible with difficulty in FIG. 5 as to how a vessel runs in the depth, i.e. runs perpendicular to the observation plane. The reason for this observation is that as a human, it is only possible to detect the required depth information by rotating the 3D data record. And this degree of rotational freedom is not available when superimposing the x-ray image with a projection of the 3D data record. The projection of the 3D data record is firmly predetermined by the current position of the C-arc system, characterized by angulation, zoom, SID (Source-Image-Distance), table position, etc.
This argument clarifies that the possibility of being able to draw the necessary depth information from the observation of a fixed projection is necessary. To this end, approaches also exist which essentially amount to stereo vision:
It is possible to display special images on a 3D monitor. A stereo effect can thus also be achieved with a fixed projection. However this is neither sufficiently pronounced, nor do current 3D monitors fulfill the demands placed on the required resolution for instance.
It is possible to observe the projected images using special colored glasses (green/red) or polarization glasses, so-called anaglyph glasses. The glasses diverge however when used during surgery.
US 2003/0156747 A1 discloses a method for displaying projection or sectional images from 3D volume data of an examination volume, with which a gray scale value of a predeterminable projection or a predeterminable section composed of individual pixels is calculated from the 3D volume data. In this way, a displacement of a voxel of the examination volume displayed by the pixel is determined for each pixel of the gray scale value at a reference plane, a colored value corresponding to the displacement is assigned to each pixel of the gray scale value and a projection and/or sectional image is displayed by superimposing or coloring the gray scale value with the colored values assigned to each pixel so that a colored depth information is obtained.